Electric discharge device



Feb. 13, 1934; A. E. NOBLE 1,946,498

I ELECTRIC DISCHARGE DEVICE Filed Nov. 15. 1929 FIGJ.

J, JJ-JJJ u I avwmtoz 406127 E. A/oA/c Patented Feb. 13, 1934 UNITED STATES PATENT OFFICE l,946,498 ELECTRIC msonanoa navroa Application November 15, 1929 Serial No. 407,413

2 Claims.

The present invention relates to a gaseous discharge luminous tube device containing a gas filling and adapted to emit light upon the discharge of electricity through the said gaseous 6 filling. The said invention relates more particularly to such a device in which the rare gas employed is relatively active, as for example, helium. When a gas such as helium is employed as the path of an electric discharge between electrodes,

as for example, iron, copper or nickel electrodes, the helium tends to be relatively rapidly destroyed so far as its capacity to conduct the current and emit light is concerned, probably due to mutual action between the gas and the cathode. Among 5 the rare gases, this tendency is more pronounced in helium than in the others and in this sense the helium is herein characterized as active. For this reason, a gaseous discharge device which depends for the most part upon helium for its effect,

has ordinarily a relatively very short life. For example, a tube containing helium at a pressure of 3 to 5 millimeters with an ordinary copper electrode has in general a very short effective life which may be, for example, 2 to 30 hours, under the influence of an electric discharge. The effective life or duration of a device of this character may be measured by passing an electric discharge through it having the requisite voltage and current characteristics necessary to cause the emission of light and observing the elapsed time between the beginning of the emission of light and the cessation thereof.

By increasing the total amount of the gas in the discharge device, as for example, by increasing the pressure of the helium to 10 to 15 millimeters, the life of the device may be greatly increased, as for example, to 1500 hours. This life however, is not sufliciently long to meet commercial demands and is attained by the sacrifice of energy and luminous efficiency inasmuch as the potential drop per unit length of gas column of a given diameter, such as 11 to 15 millimeters, is much greater at pressures corresponding to 10' to 15 millimeters of mercury, than is the case at lower pressures such as 3 to 5 millimeters of mercury.

The present invention provides a discharge device containing helium or other relatively active gas which not only has an unusually long life, but is also adapted to operate at a high efliciency,

that is to say, at such pressures that a maximum length and therefore volume of gas column may be energized by a given electric potential. This high efficiency is secured by operating between certain limits of pressure of the gaseous filling,

which in the case of helium is in the neighborhood of 3 to 5 millimeters as measured in terms of mercury in the usual way, for a tube having a diameter of 11 to 15 millimeters. The term high efliciency means and relates to that luminous efficiency which is produced by operating at or between certain limits of pressure as herein described, and the term high efficiency is to be taken as having this meaning. Notwithstandingthe use of small quantities of helium as measured by small and therefore highly efficient pressures 66 from the point of view of high luminous efficiency, the invention provides a luninous device having a greatly increased life.

The invention comprises the combination of rarified helium under certain optimum pressure 70 conditions in combination with discharge electrodes comprising a stabilized cathode. The cathode may be iron, copper, nickel, carbon or other refractory conducting substance stabilized by treatment which provides it with a coating comprising a suitable oxide of an electro-positive metal or derivative thereof.

The suboxides of electro-positive metals appear to be particularly desirable. These may be produced by providing a refractory electrode such so as copper with a coating comprising a suitable oxygen compound such as the oxide, hydroxide or peroxide of an electro-positive metal, as for example, barium peroxide, and then subjecting such coated electrode to heat to bring about re- 5 action to form decomposition or reduction products such as the suboxide of the active material, as for example barium suboxide. The term suboxide as used herein includes the products producedwhenperoxidesare thermolyzed or subjected to decomposition by heat to yield a lower oxide or suboxide.

\ The preparation of the stabilized electrode or cathode may be carried out as follows. The electrode is coated upon the inside-thereof with a coating comprising barium peroxide and is then subjected to heat whereupon the peroxide decomposes. The decomposition or thermolytic products comprise what is herein termed barium suboxide and the resulting product forms a par- 10 ticularly' stable electrode or cathode and one which in combination with the gas filling such as helium provides a discharge device having .an unusually long life such as three thouas hereinabove described, stabilization at least to some'extent, may be carried out by means of strongly electro-positive elements including those of the alkali group, as for example, potassium, caesium and the like. For example, a gaseous discharge device with a rarified helium filling at a pressure of 3 to 5 millimeters may be equipped with an anode and a cathode, the latter being provided with metallic caesium as a coating. By this means, a tube may be provided which comprises a combination of helium adapted to operate at a high energy efficiency with a stabilized cathode and possessing a moderate life, as for example, 340 hours.

Stabilization by means of alkali metals is therefore not as effective as stabilization by means of oxides as hereinabove described.

The invention will be described in greater detail with reference to the accompanying drawing which illustrates one embodiment thereof and in which Figure 1 represents a gaseous discharge luminous tube containing rarified helium at a pres* sure of 3 to 5 millimeters and provided with stabilized electrodes intended for use with alternating current and Figure 2 represents one of the electrodes in detail.

The gaseous discharge tube 1 which may have a length, between electrodes, of 17 feet and a diameter of 11 millimeters may be formed in any desired shape such as the U-shape shown in Figure 1 and is provided at each end with electrodes 2 which may in the event that alternating current is employed, be identical in form and structure inasmuch as under these conditions each electrode acts alternately as cathode and anode. The electrodes are as shown connected to the secondary 3 coil of a transformer, the primary 4 of which is adapted to be supplied with current from the generator 5. The tube 1 may be made of yellow glass and in this event is adapted to produce a decidedly yellow light. The pressure of the helium filling in the tube is carefully adjusted to correspond with that pressure at which the efflciency is at a maximum. This pressure may be for example 4 millimeters of mercury as measured in the usual way. As already described, the invention comprises the combination of helium at pressures adapted to produce high energy and luminous efliciency acting in conjunction with electrodes stabilized so that the combination yields a device having a remarkably long life.

A stabilized electrode is shown in enlarged view partly in section in Figure 2. It consists of a nickel cylinder 2 closed at one end and provided on the inside with a coating 6 comprising the thermolyzed products of a peroxide such as barium peroxide.

The operation of the invention is carried out as follows:

The tube having been provided with a helium filling and stabilized electrodes as shown is connected to the secondary of a transformer through the lead wires 7 and 8 and a discharge current of for example, 25 milliamperes, is supplied to the tube.at a potential of 15,000 volts, for example. The operation in this manner causesthe emission of a yellow or tan light when helium is employed as filling and may be continued for a period of 3,000 hours or more.

.To recapitulate, the invention comprises, in combination, a gas filling in an electric discharge luminous tube device at pressures corresponding to high energy and luminous emciency and a cathode or electrodes treated in such a manner that notwithstanding the activity of the gas and the relatively small quantity of gas employed, the cooperation between the electrode and the gas is such that high energy efficiency combined with long effective life is secured. The specific active gas preferred is helium and where helium is employed, the present invention provides a luminous tube discharge device adapted to yield light of a yellowish or tan color.

The invention furthermore comprises the combination of the features herein disclosed with a transparent yellow envelope such as yellow glass, whereby a very efficient long life yellow light may be obtained.

The advantages of the invention have been set forth in some detail and the preferred embodiments have been described. It is to be understood, however, that various changes may be 108 made without departing from the invention or sacrificing any of the advantages enumerated, or any other advantageous results which may be attained by an application of the principles and facts set forth.

To summarize, it will be noted that by employing helium at that relatively low pressure which corresponds approximately to a minimum potential drop through the gas column with respect to the internal diameter of the tube and in combination with an activated oxide cathode, that a long life high efllciency helium light is obtained, notwithstanding the relatively low helium pressure. When, furtherfore, a yellow envelope is used, a long life helium luminescent tube emitting light of a decidedly yellow color is obtained.

What I claim is:-

1. A luminescent tube adapted to emit yellow light comprising an envelope transparent to yellow rays and having an external diameter of the 126 order of 11 to 15 millimeters, a filling of helium at a pressure of the order of 3 to 5 millimeters and a cold cathode comprising the decomposition products of an alkaline earth oxygenated compound.

2. A positive column gaseous discharge tube which emits yellow light throughout a period of useful commercial life which comprises an envelope of yellow glass, a principal filling of helium, and a cold cathode comprising the decomposition product of a compound of an alkaline earth metal and oxygen.

AUBREY E. NOBLE.

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